help('modules')
#根据运行结果显示我有以下模块：
#1                   _weakref            heapq               secrets
# __future__          _weakrefset         hmac                select
# _ast                _winapi             html                selectors
# _asyncio            abc                 http                setuptools
# _bisect             aifc                idlelib             shelve
# _blake2             antigravity         imaplib             shlex
# _bootlocale         argparse            imghdr              shutil
# _bz2                array               imp                 signal
# _codecs             ast                 importlib           site
# _codecs_cn          asynchat            inspect             smtpd
# _codecs_hk          asyncio             io                  smtplib
# _codecs_iso2022     asyncore            ipaddress           sndhdr
# _codecs_jp          atexit              itertools           socket
# _codecs_kr          audioop             json                socketserver
# _codecs_tw          base64              keyword             sqlite3
# _collections        bdb                 lib2to3             sre_compile
# _collections_abc    binascii            linecache           sre_constants
# _compat_pickle      binhex              locale              sre_parse
# _compression        bisect              logging             ssl
# _csv                builtins            lxml                stat
# _ctypes             bz2                 lzma                statistics
# _ctypes_test        cProfile            macpath             string
# _datetime           calendar            macurl2path         stringprep
# _decimal            cgi                 mailbox             struct
# _dummy_thread       cgitb               mailcap             subprocess
# _elementtree        chunk               marshal             sunau
# _findvs             cmath               math                symbol
# _functools          cmd                 mimetypes           symtable
# _hashlib            code                mmap                sys
# _heapq              codecs              modulefinder        sysconfig
# _imp                codeop              msilib              tabnanny
# _io                 collections         msvcrt              tarfile
# _json               colorsys            multiprocessing     telnetlib
# _locale             compileall          netrc               tempfile
# _lsprof             concurrent          nntplib             test
# _lzma               configparser        nt                  textwrap
# _markupbase         contextlib          ntpath              this
# _md5                copy                nturl2path          threading
# _msi                copyreg             numbers             time
# _multibytecodec     crypt               opcode              timeit
# _multiprocessing    csv                 openpyxl            tkinter
# _opcode             ctypes              operator            token
# _operator           curses              optparse            tokenize
# _osx_support        datetime            os                  trace
# _overlapped         dbm                 parser              traceback
# _pickle             decimal             pathlib             tracemalloc
# _pydecimal          difflib             pdb                 tty
# _pyio               dis                 pickle              turtle
# _random             distutils           pickletools         turtledemo
# _sha1               doctest             pip                 types
# _sha256             dummy_threading     pipes               typing
# _sha3               easy_install        pkg_resources       unicodedata
# _sha512             email               pkgutil             unittest
# _signal             encodings           platform            urllib
# _sitebuiltins       ensurepip           plistlib            uu
# _socket             enum                poplib              uuid
# _sqlite3            errno               posixpath           venv
# _sre                et_xmlfile          pprint              warnings
# _ssl                faulthandler        profile             wave
# _stat               filecmp             pstats              weakref
# _string             fileinput           pty                 webbrowser
# _strptime           fnmatch             py_compile          winreg
# _struct             formatter           pyclbr              winsound
# _symtable           fractions           pydoc               wsgiref
# _testbuffer         ftplib              pydoc_data          xdrlib
# _testcapi           functools           pyexpat             xml
# _testconsole        gc                  queue               xmlrpc
# _testimportmultiple genericpath         quopri              xxsubtype
# _testmultiphase     getopt              random              zipapp
# _thread             getpass             re                  zipfile
# _threading_local    gettext             reprlib             zipimport
# _tkinter            glob                rlcompleter         zlib
# _tracemalloc        gzip                runpy
# _warnings           hashlib             sched
import math
from math import sqrt
#可以使用import导入模块，也可以使用from模块名 import 模块对象